If you would like to quickly create a new link inside the HelpCenter.io content editor, you can copy the address in your clipboard (Ctrl/Cmd + C) from anywhere, then go to the article you have been editing and select the text you would like to point to that address. Press (Ctrl/Cmd + V) to paste the address which would create a link to that address with the text that you have selected. Voilà!
Selecting the text will display the usual inline options sidebar but if you already have the address handy in your clipboard you don't have to do anything else besides pasting it over the text you would like to become your link.